In this study, we will examine the expression and regulation of EB virus in mammalian cells. Burkitt tumor cells and somatic cell hybrids of Burkitt tumor cells will be used for these studies. Attempts will be made to characterize the receptor for EBV on the surface of Burkitt/hybrid cells. Cytogenetic studies in combination with immunofluorescence and nucleic acid hybridization will be performed to study the association of the EBV genome with the cell genome and to examine virus transcription. Studies already initiated on an inhibitor of EBV (and cytomegalovirus) replication will be continued. Data obtained from these studies will help clarify the association of the EBV and cell genomes and will aid in the identification of cell surface markers which may play a role in virus infection.